The present disclosure relates to combined cardiotomy and venous return reservoirs. More particularly, it relates to cardiotomy and venous blood reservoirs with improved air handling and useful with various perfusion systems, for example in connection with patients requiring lower flow capacities.
In many surgical procedures, the functions of the heart and lungs are performed outside of the body by specialized devices such as membrane oxygenators, cardiac assist pumps, and heat exchangers. This array of equipment is operated by a perfusionist who supervises the removal and return of the patient's blood during the surgical procedure. The patient's blood is stored in a venous reservoir interposed between the vena cava tap and the pump of the heart-lung machine, which pumps the blood through the oxygenator and back into the patient's aorta. The venous reservoir also serves as a fluid butler in the external circulation system to smooth out variations between the blood flow available from the vena cava and the demands of the heart-lung machine pump. Because a substantial amount of blood escapes into the patient's chest cavity during the surgery, it is necessary to recover this cardiotomy blood from the operative field (e.g., cardiotomy suction). Once treated (e.g., filtered), the cardiotomy blood can also be returned to the patient. While the venous blood and the cardiotomy blood can be separately maintained, it has become conventional in recent years to combine the cardiotomy and venous blood into a single, hard shell cardiotomy and venous reservoir.
A conventional, combined cardiotomy and venous blood reservoir has two distinct fluid paths leading to a main chamber: a venous blood path and a cardiotomy blood path. The venous blood path enters the reservoir through a centrally located venous intake, and is conveyed into a defoaming chamber in which any air bubbles present in the venous blood are removed before the venous blood is discharged into the main chamber of the reservoir. The cardiotomy blood enters the reservoir through one or more cardiotomy inlets, and is conveyed through various filtering/defoaming regions where cellular and surgical debris and large amounts of air are removed from the cardiotomy blood.
While available filters and defoamers employed with cardiotomy and venous blood reservoirs are highly viable for performing necessary air bubble and particulate removal, in some instances concerns remain. With pediatric applications (and in particular neonates and infants), the blood volume and maximum flow rates through the surgical perfusion circuit are reduced (as compared to adult patients). Conventional (adult) cardiotomy and venous reservoirs may be less than optimal under these circumstances. For example, the reservoir blood flow path(s), while effectuating uniform flow at higher flow rates associated with adults, may introduce discontinuities at the lower flow rates of pediatric procedures, in turn causing undesirable formation of foam. In addition, the relatively small volume of blood within the reservoir (and elevated perfusion circuit cycle rate) increases the opportunities for turbulence and therefore trauma. More particularly, when the volume of blood is low in the reservoir chamber, a conventional cardiotomy and venous return reservoir will oftentimes subject the incoming blood flow to a splashing-type flow pattern, undesirably introducing trauma into the blood. Finally, while the use of defoamers to eliminate foam in the cardiotomy and venous blood within the reservoir is well-accepted, only foamed portions of the blood flow need to contact the defoamer. Conventional practice, however, entails blood flow continuously passing over/through the defoamer(s) and may lead to complications.
In light of the above, any improvements to combined cardiotomy and venous blood reservoirs will be well-received, especially those that address the concerns associated with the low volume and/or low flow rates associated with pediatric applications.